java - Why do some people use the List base class to instantiate a new ArrayList?

Question

I keep coming across code where people instantiate a new ArrayList and assign it to the List interface, like this:

List<String> names = new ArrayList<String>();

What is the reasoning behind this approach?

Answer 1

To decouple your code from a specific implementation of the interface.

This also helps you to move to another implementation of the List interface in the future.

For example -

You have List<String> names = new ArrayList<String>(); later on you decide that you should have used some other implementation of the List interface, say LinkedList so you would just change it to List<String> names = new LinkedList<String>(); and nothing breaks.